There exist different drive concepts for motor vehicles. There are thus motor vehicles with a front engine in which the front axle is permanently driven and the rear axle can be optionally driven. There are also motor vehicles in which the rear axle is permanently driven and the front axle can be optionally connected. Further, there are motor vehicles with a rear engine in which the rear axle is permanently driven and the front axle can be optionally connected by a hang-on coupling.
Document WO 2012/145580 A1 discloses a power transfer unit for selectively transferring torque from a first shaft to a second shaft by means of an activating assembly. The activating assembly includes a sliding cam, a rotating cam, an actuator for rotating the rotating cam relative to the sliding cam, and an engaging gear. The gear is configured to be moved by the sliding cam between a first engaged position where torque is transferred to a disengaged position where no torque is transferred.
From US 2010/0089685 A1 a clutch is known having two clutch parts which can be brought into engagement in form fitted manner for torque transfer. A shift member is movable in a first direction to bring the clutch parts out of engagement, an in a second direction to bring the clutch parts into engagement. A motor is provided for the movement of the shift member in the first direction and a spring element is provided for movement of the shift member in the second direction.
From DE 10 2008 037 886 A1, corresponding to WO 2010/017882 A1, a drive assembly is known for a motor vehicle driven by a plurality of axles. The drive assembly comprises a permanently driven first driveline and an optionally drivable second driveline. The optionally drivable driveline comprises a first coupling, which is arranged in the power path in front of the propeller shaft, and a second coupling which is arranged in the power path behind the propeller shaft. By opening the first and the second coupling, the propeller shaft can be switched so as to be torque-free.
DE 10 2008 063 904 A1, corresponding to WO2010/078937 A1, proposes a drive assembly for a vehicle driven by a plurality of axles. The drive assembly comprises a differential unit, a controllable hang-on coupling and a locking coupling for locking the differential movement of the differential. The two couplings are arranged coaxially relative to one another and can be actuated by a ball ramp assembly. According to one embodiment, it is proposed that first the locking coupling is actuated and then the hang-on coupling. According to a further embodiment it is proposed that first the hang-on coupling is actuated and then the locking coupling.